1. Field
The present disclosure relates generally to communication, and more specifically to techniques for channel quality feedback in multiple carrier wireless communication network.
2. Background
The 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) represents a major advance in cellular technology and is the next step forward in cellular 3G services as a natural evolution of Global system for mobile communications (GSM) and Universal Mobile Telecommunications System (UMTS). LTE provides for an uplink speed of up to 50 megabits per second (Mbps) and a downlink speed of up to 100 Mbps and brings many technical benefits to cellular networks. LTE is designed to meet carrier needs for high-speed data and media transport as well as high-capacity voice support well into the next decade. Bandwidth is scalable from 1.25 MHz to 20 MHz. This suits the needs of different network operators that have different bandwidth allocations, and also allows operators to provide different services based on spectrum. LTE is also expected to improve spectral efficiency in 3G networks, allowing carriers to provide more data and voice services over a given bandwidth. LTE encompasses high-speed data, multimedia unicast and multimedia broadcast services.
The LTE physical layer (PHY) is a highly efficient means of conveying both data and control information between an enhanced base station (eNodeB) and mobile user equipment (UE). The LTE PHY employs some advanced technologies that are new to cellular applications. These include Orthogonal Frequency Division Multiplexing (OFDM) and Multiple Input Multiple Output (MIMO) data transmission. In addition, the LTE PHY uses Orthogonal Frequency Division Multiple Access (OFDMA) on the downlink (DL) and Single Carrier—Frequency Division Multiple Access (SC-FDMA) on the uplink (UL). OFDMA allows data to be directed to or from multiple users on a subcarrier-by-subcarrier basis for a specified number of symbol periods.
Recently, LTE Advanced is an evolving mobile communication standard for providing 4G services. Being defined as 3G technology, LTE does not meet the requirements for 4G also called IMT Advanced as defined by the International Telecommunication Union such as peak data rates up to 1 Gbit/s. Besides the peak data rate, LTE Advanced also targets faster switching between power states and improved performance at the cell edge.
Multiple carriers on downlink and uplink facilitate the expanded bandwidth. However, this introduces additional feedback reporting requirements for user equipment (UE) on the uplink. Various possible combinations of downlink carrier(s) and uplink carrier(s) can complicate such feedback since overhead can be increased to report on additional bandwidth. In addition, implicit pairing of a single downlink carrier to a single uplink carrier is complicated by various implicit or explicit possibilities of pairings or groupings of carriers that would require feedback for efficient network operation.